When updating the parameters, following [1]}, we have
\(\frac{\partial L}{\partial W_{ij}} =& \left[\frac{\partial L}{\partial v_j} \frac{\partial v_j}{\partial s_j} \cdot c_{ij} +\right. \nonumber \\&+\left. \sum _{m=1}^M \left( \frac{\partial L}{\partial v_m} \frac{\partial v_m}{\partial s_m} \cdot \hat{u}_{m|i}\frac{\partial c_{im}}{\hat{u}_{m|i}}\right) \right]\cdot u_i\) 
